Luminescent tube



JuneA 9, 1931. G, E TEASDALE 1,808,826

LUMINESCENT TUBE Filed July 12, 1929 E'L- l.

gin/vento@ George E. Teasale,

mea i931 UNITED STA-TESA GEORGE E. TEASDALE, or KANSAS om, xANsAs LMINESCENT TUBE Application illed July 12, 1929. Serial No. 877,703.

My invention relates generally to luminous tubes made of transparent material such as glass andV intended to be filled with a rare atmospheric gas, such, forV instance,

as neon gas which becomes luminescent by the passage therethrough of high voltage electric currents introduced into the gas through electrodes located in the ends of the tube. The electrodes arein direct contact with the gas and connected to they inner ends of terminal wires which 'extend outwardly through the ends of the tube and are connected to the two sides of a high voltage circuit. f

When the high voltage is applied to the electrodes, the neon gas in the tube acts as a conductor and becomes brilliantly illuminated, giving off a bright orange red color which makes it very esirable for advertising and other commercial purposes, especially when the tubes are formed into letters, numbers and other designs.

Heretofore, some difficulty has been experienced with the electrodes because when made with a surface area of less than 1.5 square decimeters per ampere a phenomenon known as vaporization or spluttering takes place and is very pronounced in the presence of rare gases such as neon. The high temperature causes the electrodes to sputter at high rate so that particles of material composing the electrodes are thrown off and deposited on the Glass walls of the tube in which the electrodes are located. As the particles of material are thrown oil` they carry and pocket a certain quantity of the neon gas against the glass walls. This pocketing causes so much of the gas to be used up and its pressure so reduced, that it no longer remains conductive and the lamp becomes extinguished.

One objection to making the electrodes with a surface area of 1.5 or more square decimeters per ampere is that it necessitates making the ends of the tubes Where the electrodes are located of a much greater diameter than the rest of the tube and as the space available is very limited in a great many desi s into which some of the tubes are forme it is desirable to provide elec- Preferably, the tube 2, the stem 4 and the trodes with a surface. area of less than 1.15 square decimeters per ampere, rovided the sputtering and vaporization above refer red to can be overcome. I have succeeded in accomplishing this result by surrounding each electrode withA a reflector which projects the heat longitudinally in the tube and prevent-s the smaller electrodes from becoming overheated with consequent sputtering and vaporization.

In order that the invention ma be fully understood, reference will now be had to the accompanying drawings, in which:

Fig. 1 shows one of the tubes equipped With the invention.

Fig. 2 is a broken longitudinal section of one of the enlarged ends of the ltube equipped with an electrode and a reflector.

Fig. 3 is a cross section on line 3 3 of Fig. 2.

Referring in detail to the different parts, 2 designates a transparent tube of glass or other suitable material. Said tube is pro-V vided at each of its enlarged ends 3 with an inwardly projecting stem 4. The stems 4 are hollow at one end as indicated at 6 and provided at their other end with a shield 10 which is preferably bell-shaped and has a flaring mouth as best shown by Fig. 3.

shield 10 are cast in one piece. The shields -10 are of less diameter than the interior of the enlarged ends 3 to leave a space 12. v

14 designates two electrodes which con' sist of suitable metal or an alloy of two or more metals. Preferably, the electrodes 14 are of disk conformation and arranged within the shields 10 adjacent to the closed ends of the latter. The electrodes 14 are connected to wire conductors 16 which lead outwardly through the stems 4, in which they are hermetically sealed, so that they may be connected to a high tension circuit, not shown. The electrodes 14A preferably 95 have a surface area not exceeding 1 square decimeter per ampere, so that the enlarged surrounding ends 3 of the tube 2 may be of less diameter than usual with tubes of this character.

When the gas within the tube 2 is illumi- 109 2 l nuseas natedjby the current passing therethrough from one electrode to another the heat caused by the discharge of the current from the electrodes 14 is, to a large extent car- 6 ried away from the latter vand roected longitudinally within the tube 2 w ich, being surrounded by the outer atmosphere, is prevented from attaining a high enough temperature to crack the glass of which it `l isV referably constructed,

referably, the electrodes 14 are placed against the inner rear surfaces of the Shields 10, so that the rear surfaces 15 will have no electrode effect as is evidenced by ab- 15 sence of glow when the electrodes are charged with current and hence lthe effective electrode surface is considerablyv under 1.5 square decimeters per ampere.

While I have shown one form of electrode and one form of shield, it is to be understood l that I do not restrict myself to these particular -forms but reserve al1 rights to such chan es and modifications thereof as pro erly al1 within the spirit and scope of t e invention as claimed.

4 Having thus described my invention, what I claim and desire to secure `by Letters Patent, is:

' In combination, a transparent tube of the character described, stems extending inwardly from the outer ends of said tube, bell-shaped shields formed integral with the inner ends of said stems and rovided with 'flaring mouths, disk electro es located at the closed ends of said shields, and conductors connected to said disks.

In testimony whereof I aiix my signature.

GEORGE E. TEASDALE. 

